The present invention relates to a concrete mixing system, and more particularly relates to improvements in large portable concrete mixing systems having a mixing capacity greater than 20 cubic feet and embodying an upright mixing chamber having an inlet in the top thereof for permitting the introduction of mixture materials and an oulet at the bottom thereof for selectively permitting the discharge of a wet concrete mixture. This general type of mixer is particularly exemplified by that shown in Hall U.S. Pat. No. 3,759,492.
The features of such upright portable concrete mixing systems must resolve several factors, which inherently flow out of the competing considerations of portability and capacity, such as efficiency, installation time, cleanup time, space requirements, ease of operator access, and ease of delivery of the wet concrete mixture to transport devices.
Previous portable concrete mixers having their concrete mix materials inlet at a sufficiently low elevation to permit easy operator access thereto either sacrifice system capacity or have their concrete discharge outlet at a very low elevation with respect to the working surface. In the latter instance, such a system inevitably complicates the process of discharging the wet concrete mixture into transport devices such as trucks, carts and the like, since the low elevation of the outlet precludes the movement of transport devices upon the working surface to a position beneath the outlet. Accordingly, such systems require complex means such as conveyor belts for delivering the concrete mixture to concrete transport devices. Such delivery devices inherently require an inordinate amount of installation time, cleanup time and working space and thereby limit the mobility and efficiency of the mixing system.
Conversely, previous concrete mixing systems having their discharge outlet sufficiently spaced above a horizontal working surface as to permit the movement of transport devices upon the working surface to a position beneath the discharge outlet, either sacrifice system capacity or have their inlet spaced so far above the working surface as to preclude an operator standing upon the working surface from introducing concrete mix materials thereto. The latter systems require the time-consuming erection of a working platform to permit operator access to the mixer inlet, and/or some form of bulky elevator to raise the mixing materials to the level of the inlet.
What is needed, therefore, and what the present invention provides, is a portable upright concrete mixer having a relatively large capacity that is compact, has an inlet for introducing mixing materials located sufficiently proximate a working surface to permit easy operator access thereto, has a discharge outlet sufficiently above the working surface as to permit movement of transport devices on the working surface to a position below the outlet, and which provides enhanced portability by requiring a minimum of installation, cleanup and transport efforts.